A field was an area of land which was used for the planting of crops, similar to a meadow or pasture.
After being brought to Gamma Canaris N by the Companion in the 22nd century, Zefram Cochrane grew vegetables in fields, which were located over "that next ridge" and within walking distance of Cochrane's home. (TOS: "Metamorphosis")
In 2267, in the agricultural colony on planet Omicron Ceti III, a landing party from the USS Enterprise was given a tour of the fields and crops by the colony leader Elias Sandoval. (TOS: "This Side of Paradise")
In describing his escape during the Kazon uprising in 2346, Mabus explained that, "One minute I was a happy child playing in a field, the next an orphan exiled in space." (VOY: "Alliances")